The transesterification of lipids extracted from algae makes up the third generation of biodiesel production. The city of Logan, Utah proposes that the algae used from the 460-acre wastewater pond could potentially be used for the production of biofuel that could serve as transportation fuel for the City solid waste vehicles. Separating the algae from the Logan Lagoon wastewater is the most expensive portion of the biodiesel process and the application of chemical flocculation can significantly increase costs and potentially interfere with biodiesel production. Cross flow filtration has been identified for algae harvesting, and experiments were conducted to evaluate materials and operating conditions for separating and harvesting algae from the Logan Lagoon system.

Two cross flow filtrations units were used to conduct experiments. A pilot-scale cross flow filtration unit provided by WesTech, Inc. Engineering (Salt Lake City) with a 0.2-micron nylon membrane mesh was used for mixed-culture algae harvesting. In addition, a bench-scale cross flow filtration unit was provided, and tests were conducted to further examine the effectiveness of cross flow filtration on pure-culture algae harvesting. A 1-micron nylon, 5-micron nylon and 5-micron polyester mesh were used with this system.

The WesTech, Inc. Pilot-Scale System demonstrated that the type of membrane used was critical for effective algae harvesting. Test results showed that the algal cake that developed on the membrane and that the amount of algae harvested decreased with flux.

The bench-scale unit demonstrated that more algal cells were collected when a membrane of a larger pore size was used. The 1-micron nylon mesh proved to be the most effective at concentration algae. The 5-micron polyester mesh was shown to be more effective than the 5-micron nylon mesh.

The results in this thesis show that cross flow filtration is a feasible option for the City of Logan Environmental Department and is a technical option for algal harvesting for biofuel production.